The nation is now one day away from a deadline to raise the debt ceiling as the partial government shutdown begins Day 16. Financial markets are waiting to see if the nation can avert default as all eyes turn to the Senate.

What you need to know about the shutdown and debt limit on Wednesday, Oct. 16:

Senate back in charge after House GOP pulls bill

The burden to find a compromise now lies in the Senate, where Majority Leader Harry Reid and Minority Leader Mitch McConnell resumed control of negotiations after a frantic day in the House of Representatives. A plan by House Republicans to reopen the government and raise the nation's debt ceiling to avert default was scuttled after it became clear that Speaker John Boehner didn't have the votes to pass the measure. Some House conservatives are hoping to rein in the Affordable Care Act, but President Obama has resisted repeated efforts to undercut the health care law.

Fitch issues warning on U.S. credit rating

Fitch Ratings, the third-largest of the major debt-rating companies, warned it could possibly downgrade the nation's AAA bond rating because of the political wrangling in Washington. The Treasury Department has said the emergency measures it has been using to manage the nation's finances under the existing debt limit will run out Thursday. If the debt limit is not raised, the U.S. won't be able to borrow any more money. Fitch said it could make its decision on the rating by the end of the first quarter.

Poll: 51% say raising debt limit by deadline 'absolutely essential'

A new Pew Research Center poll says 51% of Americans believe raising the debt limit by Thursday is "absolutely essential to avoid economic crisis." By comparison, more than one-third,or 36% say the nation can go past the deadline without any "major economic problems, " the Pew survey found. That figure includes 52% of Republicans and 38% of independents who are OK with going past the deadline. White House press secretary Jay Carney has called lawmakers who are ignoring warnings about financial calamity "debt limit and default deniers."

Shutdown puts Marine Corps Marathon in 'jeopardy'

The annual Marine Corps Marathon, one of the largest races of its kind in the United States, is in "jeopardy of being canceled" because of the partial government shutdown. Notes about the status of the Oct. 27 event, which attracted 30,000 runners last year, were posted Tuesday on the marathon's website and Facebook page. Organizers said they hope to notify runners by Saturday about the race's status.

Astronauts tweet updates from space

American astronauts Karen Nyberg and Mike Hopkins have been using Twitter to keep followers up-to-date on their activities aboard the International Space Station. Nyberg, for example, tweeted on Monday a cool picture of the tip of Africa as seen from space. Their use of social media has been highlighted in recent days by NPR and Space.com. NASA is one of the federal agencies hit hardest by the shutdown, with all but 600 of its 18,000 employees on furlough. The astronauts are being supported by a skeletal crew at the space center in Houston.